Interlock control systems are commonly used on work machines such as lawn tractors, skid steer loaders, integrated tool carriers, material handling machines, backhoe loaders and the like to prevent certain operations of the machine unless certain operator parameters are met. For example, from a safety standpoint, it is advantageous and necessary to ensure that the machine operator is properly located in the machine prior to allowing movement thereof and/or prior to enabling certain systems. In the case of certain types of work machines, such as a skid steer loader, it is advantageous and necessary to ensure that the machine operator is, in fact, seated in the operator seat and that the particular operator restraint mechanism associated with such machine is in its restraining position prior to starting the machine engine, and prior to engaging or activating the drive mechanism or drive transmission and the implement control system or lift and/or tilt mechanisms. In these types of machines, interlock control systems typically include a seat sensor and/or an operator restraint sensor to selectively lockout or enable the drive transmission and the implement lift and/or tilt mechanisms. See, for example, U.S. Pat. Nos. 4,389,154; 4,955,452; 5,425,431; and 5,711,391. In all of these known interlock systems, movement of the work machine and/or activation of some or all of the above-referenced systems are prevented unless certain operator safety parameters are met, namely, that the operator is properly seated in the operator seat and/or the operator restraint mechanism is being properly used and in its restraining position.
Although the known interlock control systems provide some measure of safety to the operation of these types of work machines, under certain operational conditions, there are situations where it is undesirable to automatically engage the drive mechanism and/or implement control system just because the operator is in the seat with the arm rest or other operator restraint mechanism in its restraining position. For example, due to the particular orientation of the work machine relative to a particular work task being accomplished, the operator may not want the drive transmission and/or implement mechanism activated as soon as the seat sensor and/or operator restraint sensor senses or indicates a proper operating condition. In addition, where both the presence of the operator in the seat and the arm rest or other operator restraint mechanism has to be in its restraining position before the drive transmission and/or implement mechanisms can be activated, latent faults in either the seat switch, the operator restraint mechanism switch, or in the sensor circuit may trigger activation of such systems when only one of the two operator parameters are fulfilled. This may cause premature movement of the work machine and/or activation of the implement lift and/or tilt mechanisms. Other work scenarios may also exist where enablement of both the drive mechanism and the implement control system, simply because the operator is present in the seat and properly restrained, may not be desirable.
It is therefore desirable to provide an additional level of safety to the known interlock control systems such that once an operator is properly located in the work machine, additional steps must be taken by the operator in order to enable the drive mechanism or drive transmission and the implement control system associated with that particular machine. Under certain conditions, it is also desirable to disable the drive mechanism or transmission and set the parking brake associated with these types of work machines without disabling the implement system.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above and to providing an additional level of safety to known interlock systems.